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Television Standards Converters, Modulators etc Standards converters, modulators anything else for providing signals to vintage televisions.

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Old 18th Jul 2023, 4:34 am   #1
TonyDuell
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Default How to get teletext from an RPi -- for complete idiots

Can somebody point me to explicit instructions to generate a teletext signal using an Raspberry Pi?

Something on the level of :

1)Buy this type of RPi
2)Put these files onto an SD card of this size
(OR, write this image onto an SD card using this utility)
3) Stick the SD card into the RPi, power it up, and take the signal from the composite video socket here.

I can't easily (if at all) connect an RPi to the internet which rules out some ways of doing it. On the other hand, there should be a way to do it 'standalone'
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Old 18th Jul 2023, 10:11 am   #2
kellys_eye
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Default Re: How to get teletext from an RPi -- for complete idiots

Here's a website that takes you through it step by step:

https://www.raspberrypi.com/news/cre...etext-service/
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Old 19th Jul 2023, 10:09 am   #3
TonyDuell
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Default Re: How to get teletext from an RPi -- for complete idiots

Thanks, but a critical step in that procedure involves connecting the RPi to the internet and downloading the software. Which as I said is impossible for me.

There must be a way to do it standalone.
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Old 19th Jul 2023, 12:35 pm   #4
SiriusHardware
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Default Re: How to get teletext from an RPi -- for complete idiots

I think I probably know the answer, but do you have a modern smartphone? (I'm assuming you do have some means by which you access the internet to access this forum, although it's possible that you may use the computers in your local library / internet cafe).

Most if not all smartphones have the ability to function as a wi-fi 'hotspot' or 'Mi-Fi' which uses the phone as a bridge between any wifi equipped device and the internet, via the cellular network. It's just a feature that you have to turn on and most (possibly not all) SIM providers support it. Later models of Raspberry Pi come with wifi built onto the PCB, earlier models required something like a USB 'Nano' wifi adaptor to be plugged into one of the USB ports.

If the above is a dead end:-

Someone with Internet access and a similar R-Pi model to yours could prepare an SD card with the standard OS image and then download the required software onto it, test it, then send you the SD card to put in your own Raspberry Pi.

Possible complications: Old / Early Raspberry Pis used a standard sized SD card, later / current ones use a micro-SD sized card so there would need to be some agreement on the size, Raspberry Pi model, etc.

Output is via the composite output on the R-Pi, older/larger Pi models have an RCA composite-video output socket onboard, smaller models such as the Raspberry Pi Zero do also have composite-out but it is only supplied on a pair of solder pads to which you would have to solder a flying lead with an RCA socket on the end.

Another consideration is that if there is any 'live' teletext to be found anywhere these days it is most likely on the internet, so unless you just plan to use the project to display fixed pages of teletext (ie, as a teletext test signal generator) then you might end up needing to connect it to the internet anyway.
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Old 19th Jul 2023, 3:14 pm   #5
kellys_eye
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Default Re: How to get teletext from an RPi -- for complete idiots

Quote:
Originally Posted by TonyDuell View Post
Thanks, but a critical step in that procedure involves connecting the RPi to the internet and downloading the software.
Forgive me for stating the obvious but to load and run a Pi OS you have to go through the configuration which also sets up your internet connection (wifi) so you'd have access to download software by default.

Unless I'm missing something?
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Old 19th Jul 2023, 3:27 pm   #6
SiriusHardware
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Default Re: How to get teletext from an RPi -- for complete idiots

Not all Pis have built in wifi (The original Pi Zero (As opposed to the Pi Zero W) does not, nor do the Raspberry Pi 1 and 2) and there is no automatic assumption that the Pi will be connected via Ethernet (where the pi has ethernet) so I don't think connection to the internet is actually mandatory during the setup process.

Obtaining an image to flash the SD card with the OS with is however quite difficult without the internet, unless you buy a pre-imaged SD card from one of the several UK Raspberry Pi resellers.
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Old 20th Jul 2023, 11:59 pm   #7
hamid_1
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Default Re: How to get teletext from an RPi -- for complete idiots

I've successfully used a Raspberry Pi to generate teletext. I chose the original Raspberry Pi 1 with separate composite video phono socket. It's long since been discontinued but can be obtained secondhand. You can also use the newer models, some of which have built-in wi-fi, but you'll need a composite video cable or you'll have to solder wires onto the board for composite video.

It's rather awkward to set up without an internet connection. Typing in the command to install teletext actually downloads a script file from the internet. This goes off and downloads then installs all the necessary files. For this to work, your Raspberry Pi must be connected to the internet. Once installed, the teletext pages can be displayed offline, though if your Raspberry Pi has an internet connection, it can update the pages with the latest information. In offline mode, the teletext pages will still be transmitted, but the information in them will not get updated, so you'll see last week's news and weather if you haven't been online since then. This may not be a problem for you, of course.

As said, you can turn a modern mobile phone into a wi-fi 'hotspot' by switching on that feature in the settings. This is how I'm accessing the internet right now. I don't currently have fixed-line broadband at my house. The phone produces a wi-fi signal just like a wireless router with fixed-line broadband, except that it's mobile and can be used wherever there's a mobile phone signal. Simply connect your PC or Raspberry Pi to your mobile wi-fi and off you go! If you use this method, there are a few things to bear in mind:

The Raspberry Pi 1 does not have built-in wi-fi. There are two versions of the Raspberry Pi 1 - 'B' which has wired ethernet and 'A' which does not. Either of them will work for teletext. To use wi-fi you'll need to plug in a USB wireless network adapter that's compatible with Raspberry Pi OS. I got lucky and tried a random USB wi-fi adaptor that I had lying around. It worked straightaway without needing any drivers. I guess a large number of wi-fi adapters are supported these days.

Secondly, if you are using the mobile network to access the internet, be aware of how much data allowance is included in your plan and the costs of going over it, which can be very high. Downloading a Raspberry Pi OS image could take a couple of gigabytes, and downloads can be slow at times. You can get Pay As You Go SIM cards from mobile phone shops or newsagents / convenience stores. Typically when you buy £10 of credit, you can get a bundle of call-time minutes and several gigabytes of data valid for one month with no commitment to pay anything more. This should be enough to set up a Raspberry Pi with teletext.

If you get stuck I can make you a copy of my Raspberry Pi 1 full-size SD card with teletext software already installed. I'd have to send it to you by post though, the file will be too big to attach here. Also I can't guarantee that it will work on a newer Raspberry Pi model.

Once you have the Raspberry Pi with teletext software up and running, you either connect the composite video from the Raspberry Pi directly into your TV's AV input and select AV mode on your TV, or connect the composite video to a UHF RF modulator connected to the aerial socket on your TV. Tune the TV into the RF modulator's signal. You should see the Raspberry Pi picture on your TV. Select the telextext service you want to run on the Raspberry Pi teletext software (currently there's Ceefax and Teefax). Press the TEXT button on your TV remote control and enjoy teletext!
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Old 21st Jul 2023, 8:28 am   #8
SiriusHardware
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Default Re: How to get teletext from an RPi -- for complete idiots

Tony has explained elsewhere that his internet facilities at home are extremely limited. I understand that his current Pi is one of the older ones (Pi 2?), ie, with composite out available on a single RCA connector and the large sized SD card holder, but it would be good if Tony could definitely confirm this.

I think what would probably help him most would be an actual SD card already imaged with a working teletext setup on it. Card image files tend to be quite large (several Gigabytes) and that will be too much.

Last edited by SiriusHardware; 21st Jul 2023 at 8:35 am.
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Old 3rd Jan 2024, 12:05 am   #9
Studio263
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Default Re: How to get teletext from an RPi -- for complete idiots

Would this method be the basis of how this was done?

www.ebay.co.uk/itm/145531149754

These results seem to have been generated by an excellent system which downloads pages from somewhere and puts them onto a UHF carrier so that it can be decoded by the complete circuits in the television (or adaptor in this case). Unfortunately the seller gives no details of how it works.

I was wondering also how one would connect the modulator to the CVBS output of the RPi. Some background reading on Teletext suggests that careful filtering was required to round the edges of the digital waveform by just the right amount to prevent the limited HF response of the receiver's IF strip from distorting the signal.

The other question I have is whether it is possible to genlock the RPi to another video source so that Teletext data can be correctly inserted in the sync period of a picture sourced from a Freeview receiver (etc), so that the system operates exactly in its original manner.
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Old 3rd Jan 2024, 11:26 pm   #10
hamid_1
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Default Re: How to get teletext from an RPi -- for complete idiots

Yes - I have done the same thing. Instead of a vintage standalone teletext decoder (as shown in the auction link) I used an old Sony Trinitron TV/VHS combi set with built-in teletext decoder. A Raspberry Pi computer generates the up-to-date pages from Ceefax.

The up-to-date pages from Ceefax come from a server run by a teletext enthusiast called Nathan Dane in Northern Ireland. In a nutshell, Nathan wrote a script which automatically copies news, weather and other information from the BBC website then converts it into Ceefax pages. To bring Ceefax back into your home, all you need is a Raspberry Pi running some teletext generating software. The Raspberry Pi connects to the internet, retrieves the pages from Nathan's server and encodes them into teletext via the Raspberry Pi's Composite Video Out. You then connect the composite video to your vintage teletext TV or teletext decoder, either directly or via RF modulator if necessary. In my case, the Sony TV VCR had composite video input so a modulator was not needed, but a Maplin RF modulator has been reported to work.

Once you have set up everything, Ceefax works just like it used to before analogue TV was switched off. It's almost like the digital switchover never happened.

A detailed story of the development of Nathan's Ceefax service is on his website: https://www.nathanmediaservices.co.u...iewer/history/

It's possible to insert the teletext signal into an existing video signal such as live TV. This requires additional hardware, described in the link.

You can also view the live Ceefax pages online without needing a Raspberry Pi or a vintage TV, just use your web browser: https://www.nathanmediaservices.co.uk/teletext-viewer/

The site used to give instructions to install the software on your own Raspberry Pi. Initially I tried it but had some problems with it not installing properly, then I tried again using an older version of the Raspberry Pi OS and that worked. I emailed the author but received no response. That was about 2 years ago. Now I can't find the software for download on his site. This is a problem, since websites like this are run as a hobby, they can go down at any time. Luckily, once you have the Raspberry Pi teletext generating software, it will continue to work if the server goes down and even works without an internet connection. The only issue will be that the generated pages will not get updated.
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Old 3rd Jun 2024, 11:44 pm   #11
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Default Re: How to get teletext from an RPi -- for complete idiots

The software that Nathan uses is from my project vbit2. You should be able to install and generate a Ceefax service on all Raspberry Pi versions, except Pi400 and Pi5. The Wiki explains how to install vbit2. https://github.com/peterkvt80/vbit2/wiki

It isn't practical to install the teletext software without an internet connection. My advice is to take your Pi round to a friend's house and get it up and running on their internet. After that it will run just fine without any internet.

Any problems, please ask me.
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